#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>

#define STACK_MAX_SIZE 20
typedef float T;

typedef struct Stack_tag {
    T *data;
    size_t size;
    size_t top;
} Stack_t;

Stack_t* createStack() {
    Stack_t *out = NULL;
    out = malloc(sizeof(Stack_t));
    if (out == NULL) {
        exit(-1);
    }
    out->size = 10;
    out->data = malloc(out->size * sizeof(T));
    if (out->data == NULL) {
        free(out);
        exit(-1);
    }
    out->top = 0;
    return out;
}

void deleteStack(Stack_t **stack) {
    free((*stack)->data);
    free(*stack);
    *stack = NULL;
}

void resize(Stack_t *stack, size_t new_size) {
    if (stack->size == new_size) {
        return;
    } else if (stack->size < new_size) {
        stack->size = new_size;
        stack->data = realloc(stack->data, new_size * sizeof(T));
        if (stack->data == NULL) {
            exit(-1);
        }
    } else if (stack->top <= new_size) {
        stack->size = stack->top;
        stack->data = realloc(stack->data, stack->size * sizeof(T));
    } else {
        exit(-1);
    }
}

void implode(Stack_t *stack) {
    resize(stack, stack->top);
}

void push(Stack_t *stack, T value) {
    if (stack->top >= stack->size) {
        resize(stack, stack->size * 2);
    }
    stack->data[stack->top] = value;
    ++stack->top;
}

T pop(Stack_t *stack) {
    if (stack->top == 0) {
        exit(-1);
    }
    --stack->top;
    return stack->data[stack->top];
}

T front(const Stack_t *stack) {
    if (stack->top <= 0) {
        exit(-1);
    }
    return stack->data[stack->top - 1];
}

int main() {
    int i;
    Stack_t *s = createStack();

    for (i = 0; i < 300; i++) {
        push(s, i);
    }
    implode(s);
    for (i = 0; i < 300; i++) {
        printf("%f ", front(s));
        printf("%f ", pop(s));
    }

    deleteStack(&s);
}